On Mon, 02 Jul 2001 01:51:41 +0200, Tor Olav Kristensen wrote:
>
>Ron Parker wrote:
>>...
>> You want atan2(vlength(vcross(A-B,C-B)),vdot(A-B,C-B)).
>
>Yes, that's one way of doing it.
>
>
>He could also try this:
>acos(vdot(vnormalize(A-B),vnormalize(C-B)))
>
>or even:
>asin(vlength(vcross(vnormalize(A-B),vnormalize(C-B))))
>
>But I would suspect POV to parse your expression faster.
>Is this true Ron ?

I suspect they're all about the same in parsing time.  I chose atan2 because
it automatically handles angles beyond pi/2, but that might not be an issue
in this case if you use acos.  asin would have a problem.

-- 
#macro R(L P)sphere{L F}cylinder{L P F}#end#macro P(V)union{R(z+a z)R(-z a-z)R(a
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g)#end#macro Z(D a T F)union{P(a)P(-a)R(y-z-1a)translate.1*D-y*8pigment{rgb<S(7)
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